The previous six -- including the Titans' Chris Johnson -- never reached that milestone again, leaving Peterson and Johnson as the only active players with a chance to make history by achieving the feat twice.

At the beginning of every season since his 2,000-yard campaign of 2009, Johnson receives the obligatory queries about whether he can do it again.

"Every year, my goal is to rush for 2,000 yards," the sixth-year back said matter-of-factly following Monday’s training camp session at Saint Thomas Sports Park."I already did it once," he added, "so I really can’t go back and lower my standards to lower than that."

But has joining the likes of Peterson (2,097 yards in 2012), Eric Dickerson (2,105 in 1984), Jamal Lewis (2,066 in 2003), Barry Sanders (2,053 in 1997), Terrell Davis (2,008 in 1998) and O.J. Simpson (2,003 in 1973) become an albatross around Johnson's neck?

With his good, but short of elite production from recent years, some wonder if setting the 2K goal each season is unrealistic, considering no back has ever done it twice.

"When he came into the league and he was running for five or six yards a carry, everyone assumes that's how easy it is," Titans coach Mike Munchak said of Johnson. "But this league isn’t that way. He got his 2,000. It just gets harder when you do that."

Certainly, what Johnson has achieved in five seasons is remarkable, including starting 77 of 79 games. As a 2008 first-rounder, he has rushed for 6,888 yards -- second-best in the league for the period -- while standing as only the sixth back in NFL history to gain that many yards in their initial five seasons.

Johnson has already moved to third on the franchise’s all-time rushing list -- trailing only Hall of Famer Earl Campbell and former Heisman Trophy winner Eddie George -- in rushing yards, rushing touchdowns and 100-yard rushing games.

In 2010, Johnson followed up the 2K campaign with 1,364 rushing yards. In 2011, after coming off a contract holdout that had him arriving late to training camp after signing a four-year, $53 million extension, he posted a career-low 1,047 yards.

In 2012, Johnson rushed for 1,243 yards and six touchdowns.

Granted, the Titans offensive line was decimated by injuries and stung by lack of productivity by reserves. But Johnson also showed signs of slowing, losing some explosion of recent years. In 2012, he rushed for more than 100 yards only five times, including a season-high 195 at Buffalo, but he also didn't surpass 60 rushing yards eight times.

"It really doesn't matter to me because I know what I can do," said Johnson. "I know I come in every day and work hard. You know you are always going to have naysayers out there, and people can say what they want to say.

"But at the end of the day, they just need something to talk about. So, I don’t really worry about those things."

Johnson likes how the Titans fortified their offensive line during the offseason -- signing guard Andy Levitre and drafting Chance Warmack in Round 1. Plus, Tennessee strengthened the backfield by acquiring Shonn Greene, a bullish runner signed through free agency after he eclipsed 1,000 yards the past two seasons for the Jets.

But the Titans didn’t stop there. After playing various positions last season, veteran Fernando Velasco returns at center. But he could be pushed by fourth-round draft pick Brian Schwenke, who has been slowed by a hamstring injury. Tennessee also signed veteran interior lineman Rob Turner, who started all 16 games for the Rams last season, to go with veteran backups Mike Otto on the inside and Byron Stingily at either tackle.

"They are coming together pretty good," Johnson said of the offensive line. "They are working hard every day and just trying to jell together and just continue to get better and better every day."

Munchak likes what he has seen from Johnson in training camp and heading into Thursday night’s preseason opener against the Redskins. The Titans open the season Sept. 8 at Pittsburgh.

"(Johnson is) running well," Munchak said. "He's excited about what we're doing. We gave him one day to rest, so he's been out here every other day doing everything we've asked him to do. So far, so good.

As for the 2,000 rushing yards, Johnson was complimentary of Peterson, who accomplished the feat one year removed from major knee surgery. But Johnson still considers himself among the game’s elite running backs.

"(Opponents) still know what type of player they are going against," Johnson said. "Another guy just did it -- 2,000 yards last year -- so they are going to talk about him a lot and do all those things. And it’s well worth it. He did a good thing."

Munchak has no problem with his star back setting such lofty individual goals.

"No one’s ever (rushed for 2,000 yards) again for a reason," said Munchak, a member of the Pro Football Hall of Fame as an offensive lineman. "So I’m glad his expectations are high -- the higher, the better. We’re expecting to have a big year and we’ll see what happens. So, if he runs the ball well, we’re going to have a good year.

"So, we need to start off at the beginning where we can’t waste four or five weeks to get it going. We know that. So we need to come out of the box running well."